Etching isolation features and dense features within a substrate

ABSTRACT

Systems and methods for etching different features in a substantially equal manner are described. One of the methods includes applying a low frequency bias signal during a low TCP state and applying a high frequency bias signal during a high TCP state. The application of the low frequency bias signal during the low TCP state facilitates generation of hot neutrals, which are used to increase an etch rate of etching dense features compared to an etch rate for etching isolation features. The application of the high frequency bias signal during the high TCP state facilitates generation of ions to increase an etch rate of etching the isolation features compared to an etch rate of etching the dense features. After applying the low frequency bias signal during the low TCP state and the high frequency bias signal during the high TCP state, the isolation and dense features are etched similarly.

CLAIM OF PRIORITY

This application is a national stage filing of and claims priority,under 35 U.S.C. § 371, to PCT/US2019/062862, filed on Nov. 22, 2019, andtitled “ETCHING ISOLATION FEATURES AND DENSE FEATURES WITHIN ASUBSTRATE”, which claims priority, under 35 U.S.C. § 119(e), to U.S.Provisional Application No. 62/775,735, filed on Dec. 5, 2018, andtitled “ETCHING ISOLATION FEATURES AND DENSE FEATURES WITHIN ASUBSTRATE”, both of which are incorporated by reference herein in theirentirety.

FIELD

The present embodiments relate to systems and methods for etchingisolation and dense features within a substrate.

BACKGROUND

The background description provided herein is for the purposes ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent it is described in thisbackground section, as well as aspects of the description that may nototherwise qualify as prior art at the time of filing, are neitherexpressly nor impliedly admitted as prior art against the presentdisclosure.

In a plasma tool, a radio frequency (RF) generator supplies power. Thepower is supplied to a plasma chamber. In the plasma chamber, asubstrate is being processed. When the power is supplied, plasma isgenerated within the plasma chamber to process different features of thesubstrate.

It is in this context that embodiments described in the presentdisclosure arise.

SUMMARY

Embodiments of the disclosure provide systems, apparatus, methods andcomputer programs for etching isolation and dense features within asubstrate. It should be appreciated that the present embodiments can beimplemented in numerous ways, e.g., a process, an apparatus, a system, adevice, or a method on a computer readable medium. Several embodimentsare described below.

In one embodiment, a method for generating hot neutrals is described.The hot neutrals are generated to achieve comparable etch rates in boththe isolation and dense features of a substrate. In the method, low biaspower, such as less than 10 watts is applied with a low bias frequencyand a high bias power, such as greater than 100 watts is applied at ahigher bias frequency. Also, in the method, the low bias frequency isapplied with low transformer coupled plasma (TCP) power, such as lessthan 60 watts, and the higher bias frequency is applied with a high TCPpower, such as greater than 100 watts. The hot neutrals are generatedwhen the low bias power and the low TCP power are applied and the hotneutrals facilitate increasing etch rate of the dense features tocompensate for higher etch rate of the isolation features during thehigh bias power, the higher bias frequency, and the high TCP power. Thehigher etch rate of the isolation features is achieved during the highbias power, the higher bias frequency, and the high TCP power due to awider opening of the isolation features compared to the dense features.An example of the low bias frequency is a frequency that is less than 2megahertz (MHz) and an example of the higher bias frequency is afrequency that is greater than 10 MHz. As an example, the high biaspower, the higher bias frequency, and the high TCP power has a total ofduty cycle less than 20% and the low bias power, the low bias frequency,and the low TCP power has a duty cycle greater than 80%. The hotneutrals will have a longer time to etch the dense features tocompensate for the higher etch depth of the isolation features.

When the low bias power is applied with the low bias frequency and thelow TCP power after the high bias power and the higher bias frequencyand the high TCP power are applied, ion temperature drops because of thelow TCP power. The drop in the ion temperature reduces ion angularspread causing ions to penetrate small openings of the dense features toenhance an etch rate of the dense features. Also, because of the low TCPpower, electron temperature drops and the drop in the electrontemperature produces electron attachment reactions to create a largenumber of negative ions. Low energy of electrons favor the electronattachment reactions over other processes because dissociation,ionization or excitation of molecules/radicals demand higher energy.Positive ions that bombard the substrate with energy have collisionswith the negative ions in a pre-sheath region causing neutralizationreactions and producing the hot neutrals. The low energy electrons stillcan have sufficient energy to produce vibrationally excited moleculesand can generate the hot neutrals with successive electron impacts basedon the Franck-Condon principle. Also, during charge exchange reactions,a neutral can gain charge from an ion and the ion becomes a directionalhot neutral after donating the charge. A continuous wave bias voltage atany radio frequency (RF) bias frequency cannot produce sufficient hotneutrals but vibrational excitation and the neutralization reactions canproduce a substantial density of isotropic hot neutrals. Also,directional hot neutrals are generated by the charge exchange reactions.

When the high bias power and the higher bias frequency and the high TCPpower are applied, ions with high energy dominate a plasma process inwhich ions easily enter wider openings of the isolation features. Theions etch the isolation features more compared to the dense features.Wider openings or isolated features also can have an advantage ofreceiving more radicals through their larger openings, which helps toincrease their etching. However, when the high bias power and the higherbias frequency and the high TCP power are applied, there is a higheramount of growth of a passivation layer at a bottom surface of theisolation features compared to a bottom surface of the dense features.This is because the isolation features invite more radicals to passivateits bottom surface due to the wider openings compared to the densefeatures, which have narrower openings. The dense features are primarilyetched by directional enough ions to enter their narrower trenchopenings when the high bias power, the higher bias frequency and thehigh TCP power are applied. Such smaller openings allow a lower radicalor neutral flux to passivate dense feature bottoms. Since the hotneutrals generated during a low bias power, a low TCP and a low biasfrequency state are weak etching agents, they can etch silicon withinthe substrate slowly and a higher etching threshold passivated layer ofthe substrate is etched at a much slower rate. When the low bias poweris applied with the low bias frequency and the low TCP power, because ofless passivation at the bottom surface of the dense features, etch rateof the dense feature increases compared to that of the isolationfeatures with a thicker passivated layer. Also, when the low bias poweris applied with the low bias frequency and the low TCP power, etch rateof the isolation features drops due to the higher amount of passivation.The higher amount of passivation protects the isolation features becausethe hot neutrals are weak etchers and cannot clear a passivation layerat the bottom of the isolation features quickly. Since the etch rate ofthe dense feature is enhanced compared to the etch rage of the isolationfeature during the low bias power, low TCP and low frequency state, atthe end of a complete RF bias cycle, etch depths of both the isolationfeatures and the dense features become equal or very comparable. Itshould be noted that the terms isolation features and isolated featuresare used herein interchangeably.

In an embodiment, a method for etching isolation and dense featureswithin a substrate is described. The method includes supplying a lowfrequency bias RF signal to a first impedance matching circuit,supplying a high frequency bias RF signal to the first impedancematching circuit, and pulsing a TCP RF signal between a low TCP stateand a high TCP state to provide the TCP RF signal to a second impedancematching circuit. The low frequency bias RF signal is supplied duringthe low TCP state to etch the dense features and the high frequency biasRF signal is supplied during the high TCP state to etch the isolationfeatures.

In one embodiment, a system for etching isolation and dense featureswithin a substrate is described. The system includes a low frequency RFgenerator configured to supply a low frequency bias RF signal to a firstimpedance matching circuit and a high frequency RF generator configuredto supply a high frequency bias RF signal to the first impedancematching circuit. The system includes a TCP RF generator configured topulse a TCP RF signal between a low TCP state and a high TCP state toprovide the TCP RF signal to a second impedance matching circuit. Thelow frequency bias RF signal is supplied during the low TCP state toetch the dense features and the high frequency bias RF signal issupplied during the high TCP state to etch the isolation features.

In an embodiment, a controller for etching isolation and dense featureswithin a substrate is described. The controller includes one or moreprocessors configured to control a low frequency RF generator to supplya low frequency bias RF signal to a first impedance matching circuit.The one or more processors are further configured to control a highfrequency RF generator to supply a high frequency bias RF signal to thefirst impedance matching circuit and control a TCP RF generator to pulsea TCP RF signal between a low TCP state and a high TCP state and toprovide the TCP RF signal to a second impedance matching circuit. Theone or more processors are further configured to control the lowfrequency RF generator to supply the low frequency bias RF signal duringthe low TCP state to etch the dense features. The one or more processorsare configured to control the high frequency RF generator to supply thehigh frequency bias RF signal during the high TCP state to etch theisolation features. The controller includes a memory device coupled tothe one or more processors. The memory device is configured to store aparameter level for the low TCP state and a parameter level for the highTCP state.

Some advantages of the herein described systems and methods includeetching the dense and isolation features of the substrate in asubstantially equal manner During a low TCP state, the low TCP power isapplied and during a high TCP state, the high TCP power is applied. Withthe low TCP state, the low bias frequency and the low bias power areapplied. Similarly, with the high TCP state, the higher bias frequencyand the high bias power are applied. The application of the low biasfrequency and the low bias power in the low TCP state facilitatesgeneration of the hot neutrals. The hot neutrals increase an etch rateof etching the dense features compared to etching the isolationfeatures. The application of the higher bias frequency and the high biaspower in the high TCP state facilitates generation of ions. The ionsincrease an etch rate of etching the isolation features compared toetching the dense features. As such, by applying the low bias frequencyand the low bias power in the low TCP state and the higher biasfrequency and the high bias power in the high TCP state, both theisolation and dense features are etched substantially equally.

Other aspects will become apparent from the following detaileddescription, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments may best be understood by reference to the followingdescription taken in conjunction with the accompanying drawings.

FIG. 1 is a diagram of an embodiment of a system to illustrate anapplication of low frequency bias pulsing during a low transformercoupled plasma (TCP) state and high frequency bias pulsing during a highTCP state.

FIG. 2A is an embodiment of a graph to illustrate a logic level of adigital pulse signal versus time t.

FIG. 2B is a diagram of an embodiment of a graph to illustrate a radiofrequency (RF) signal that is generated by an RF power supply PSA of anRF generator of FIG. 1.

FIG. 2C is an embodiment of a graph to illustrate a logic level of adigital pulse signal versus the time t.

FIG. 2D is a diagram of an embodiment of a graph to illustrate an RFsignal that is generated by an RF power supply PSB of another RFgenerator of FIG. 1.

FIG. 2E is an embodiment of a graph to illustrate a logic level of adigital pulse signal versus the time t.

FIG. 2F is a diagram of an embodiment of a graph to illustrate an RFsignal that is generated by an RF power supply PSC of yet another RFgenerator of FIG. 1.

FIG. 2G is an embodiment of a graph to illustrate a clock signal versusthe time t.

FIG. 3A is an embodiment of a graph to illustrate a logic level of adigital pulse signal versus the time t.

FIG. 3B is a diagram of an embodiment of a graph to illustrate an RFsignal that is generated by the RF power supply PSA.

FIG. 3C is an embodiment of a graph to illustrate a logic level of adigital pulse signal versus the time t.

FIG. 3D is a diagram of an embodiment of a graph to illustrate an RFsignal that is generated by the RF power supply PSB.

FIG. 4A is an embodiment of a graph to illustrate a logic level of adigital pulse signal versus the time t.

FIG. 4B is a diagram of an embodiment of a graph to illustrate an RFsignal that is generated by the RF power supply PSA.

FIG. 4C is an embodiment of the graph of FIG. 3C.

FIG. 4D is an embodiment of the graph of FIG. 3D.

FIG. 5 is a diagram to illustrate chemical reactions among a processgas, electrons that are generated during a low TCP state and a low biasstate, and ions that are generated during a high TCP state and a highbias state.

FIG. 6A is an embodiment of an embodiment of a graph to illustrate anangular spread of hot neutrals across a surface of a substrate when acontinuous bias voltage is applied to a substrate support.

FIG. 6B is a diagram of an embodiment of a graph to illustrate anangular spread of hot neutrals across the surface of the substrate whena pulsed bias voltage is applied to the substrate support.

FIG. 6C is a diagram of an embodiment of a graph to illustrate anincreased directionality of hot neutrals across the surface of thesubstrate when the pulsed bias voltage is applied to the substratesupport.

FIG. 7A is a diagram of an embodiment of a substrate to illustratedepths of isolation features and dense features after the high TCP stateand the high bias state.

FIG. 7B is a diagram of an embodiment of the substrate of FIG. 7A afterapplying the low TCP state and the low bias state.

FIG. 7C is a diagram of an embodiment of the substrate of FIG. 7A afterapplying the low TCP state and the low bias state.

FIG. 7D is a diagram of an embodiment of the substrate of FIG. 7A afterapplying the low TCP state and the low bias state.

DETAILED DESCRIPTION

The following embodiments describe systems and methods for etchingisolation and dense features within a substrate. It will be apparentthat the present embodiments may be practiced without some or all ofthese specific details. In other instances, well known processoperations have not been described in detail in order not tounnecessarily obscure the present embodiments.

FIG. 1 is a diagram of an embodiment of a system 100 to illustrate anapplication of low frequency bias pulsing with during a low transformercoupled plasma (TCP) state and high frequency bias pulsing during a highTCP state. The system 100 includes radio frequency (RF) generators RFGA,RFGB, and RFGC, an impedance match 104, another impedance match 108, aplasma chamber 114, a host computer 112. Examples of the host computer112 include a desktop computer, laptop computer, a server, a controller,a tablet, and a smart phone. The RF generator RFGC is sometimes referredto herein as a TCP RF generator.

An impedance match, as described herein, includes a network of one ormore resistors, or one or more capacitors, or one or more inductors, ora combination thereof, to match an impedance of a load coupled to anoutput of the impedance match with an impedance of a source coupled toan input of the impedance match. Examples of a load coupled to an outputO1 of the impedance match 104 include the plasma chamber 114 and an RFtransmission line 116. Moreover, examples of a source coupled to inputsI1 and I2 of the impedance match 104 include an RF cable 118A, anotherRF cable 118B, the RF generator RFGA, and the RF generator RFGB.Similarly, examples of a load coupled to an output of the impedancematch 108 include the plasma chamber 114 and an RF transmission line120. Moreover, examples of a source coupled to an input of the impedancematch 108 include an RF cable 122 and the RF generator RFGC. It shouldbe noted that the terms impedance match, an impedance matching circuit,and an impedance matching network are used herein interchangeably.

The host computer 112 includes a processor 124 and a memory device 126.The processor 124 is coupled to the memory device 126. As used herein, aprocessor is an application specific integrated circuit (ASIC), or aprogrammable logic device (PLD), or a central processing unit (CPU), ora microprocessor, or a microcontroller. Examples of a memory deviceinclude a random access memory (RAM) and a read-only memory (ROM). Toillustrate, a memory device is a flash memory, a hard disk, or a storagedevice, etc. A memory device is an example of a computer-readablemedium.

The plasma chamber 114 includes a substrate support 128 on which asubstrate S is placed for processing. The plasma chamber 114 furtherincludes a dielectric window 130. Examples of the substrate support 128include a chuck and a wafer platen. The chuck can be, for example, anelectrostatic chuck. The substrate support 128 includes a lowerelectrode, which is made from a metal, such as aluminum or an alloy ofaluminum. A transformer coupled plasma (TCP) coil is situated outsidethe plasma chamber 114 over the dielectric window 130.

The RF generator RFGA includes a digital signal processor DSPA andmultiple parameter controllers PRAS(n−N), PRAS(n−1), through PRAS(n),where n is an integer greater than zero and greater than N, and N is aninteger. As an illustration, n is 3 and N is 2. Examples of a parameter,as used herein, include voltage and power. As used herein, a controlleris ASIC, or a PLD, or a CPU, or a microprocessor, or a microcontroller,or a processor, or includes a processor and a memory device. Theprocessor of the controller is coupled to the memory device of thecontroller. The RF generator RFGA further includes a frequencycontroller FCA. The RF generator RFGA further includes a driver systemDRVRA and an RF power supply PSA. The power supply PSA is sometimesreferred to herein as a low frequency RF power supply. An example of adriver system, as used herein, includes one or more transistors. Anotherexample of the driver system, as used herein, includes one or moretransistors that are coupled to an amplifier.

An example of the RF power supply, as used herein, include an RFoscillator that generates a sinusoidal signal at a radio frequency, suchas ranging from and including 300 kilohertz (kHz) to 100 megahertz (100MHz). For example, the RF power supply PSA generates an RF signal 102Ahaving a low frequency that is less than or equal to 2 MHz. For example,the RF signal 102A can range from 300 kHz to 2 MHz. To illustrate, theRF power supply PSA operates at the low frequency of 400 kHz or of 2MHz. The RF signal 102A is sometimes referred to herein as a lowfrequency bias RF signal.

The processor 124 is coupled to the digital signal processor DSPA via atransfer cable 132A. Examples of a transfer cable, as used herein,include a coaxial cable that is used to transfer data in a parallelmanner, a cable that is used to transfer data in a serial manner, and auniversal serial bus (USB) cable. The digital signal processor DSPA iscoupled to the parameter controllers PRAS(n−N) through PRAS(n) and tothe frequency controller FCA. Each of the parameter controllersPRAS(n−N) through PRAS(n) and the frequency controller FCA is coupled tothe driver system DRVRA and the driver system DRVRA is coupled to the RFpower supply PSA. The RF power supply PSA is coupled via the RF cable118A to the input I1 of the impedance match 104. The output O1 of theimpedance match 104 is coupled to the substrate support 128.

Similarly, the RF generator RFGB includes a digital signal processorDSPB and multiple parameter controllers PRBS(n−N), PRBS(n−1), throughPRBS(n), where n is an integer greater than zero and greater than N, andN is an integer. The RF generator RFGB further includes a frequencycontroller FCB. The RF generator RFGB also includes a driver systemDRVRB and the RF power supply PSB. The power supply PSB is sometimesreferred to herein as a high frequency RF power supply. As an example,the RF power supply PSB generates an RF signal 102B having a highfrequency that is greater than or equal to 10 MHz. For example the highfrequency can range from 10 MHz to 65 MHz. To further illustrate, the RFpower supply PSB operates at the high frequency of 27 kHz or of 60 MHz.The RF signal 102B is sometimes referred to herein as a high frequencybias RF signal.

The processor 124 is coupled to the digital signal processor DSPB via atransfer cable 132B. The digital signal processor DSPB is coupled to theparameter controllers PRBS(n−N) through PRBS(n) and to the frequencycontroller FCB. Each of the parameter controllers PRBS(n−N) throughPRBS(n) and the frequency controller FCB is coupled to the driver systemDRVRB and the driver system DRVRB is coupled to the RF power supply PSB.The RF power supply PSB is coupled via the RF cable 118B to the input I2of the impedance match 104.

The RF generator RFGC includes a digital signal processor DSPC andmultiple parameter controllers PRCS(n−N), PRCS(n−1), through PRCS(n),where n is an integer greater than zero and greater than N, and N is aninteger. The RF generator RFGC further includes a frequency controllerFCC. The RF generator RFGC includes a driver system DRVRC and an RFpower supply PSC. The RF power supply PSC is sometimes referred toherein as a TCP RF power supply.

The processor 124 is coupled to the digital signal processor DSPC via atransfer cable 132C. The digital signal processor DSPC is coupled to theparameter controllers PRCS(n−N) through PRCS(n) and to the frequencycontroller FCC. Each of the parameter controllers PRCS(n−N) throughPRCS(n) and the frequency controller FCC is coupled to the driver systemDRVRC and the driver system DRVRC is coupled to the RF power supply PSC.The RF power supply PSC is coupled via the RF cable 122 to the input ofthe impedance match 108. The output of the impedance match 108 iscoupled via the RF transmission line 120 to a TCP coil 134 that islocated above the dielectric window 130.

The processor 124 generates a clock signal, which is described belowwith reference to FIG. 2G. Moreover, the processor 124 generates adigital pulse signal 136A and provides the digital pulse signal 136A tothe digital signal processor DSPA. The digital pulse signal 136A issynchronized with reference to the clock signal in a manner describedbelow. The digital pulse signal 136A is supplied via the transfer cable132A to the digital signal processor DSPA.

Upon receiving the digital pulse signal 136A, the digital signalprocessor DSPA identifies an occurrence of a state of the digital pulsesignal 136A. For example, when the digital pulse signal 136A has fourstates S1, S2, S3, and S4 during an occurrence of a clock cycle of theclock signal, the digital signal processor DSPA determines whether alogic level of the digital pulse signal 136A is 0, 1, 2, or 3. Upondetermining that the logic level of the digital pulse signal 136A is 1,the digital signal processor DSPA identifies an occurrence of the stateof the digital pulse signal 136A to be S1. Similarly, upon determiningthat the logic level of the digital pulse signal 136A is 2, the digitalsignal processor DSPA identifies an occurrence of the state of thedigital pulse signal 136A to be S2. Also, upon determining that thelogic level of the digital pulse signal 136A is 3, the digital signalprocessor DSPA identifies an occurrence of the state of the digitalpulse signal 136A to be S3. Moreover, upon determining that the logiclevel of the digital pulse signal 136A is 0, the digital signalprocessor DSPA identifies an occurrence of the state of the digitalpulse signal 136A to be S4.

As another example, when the digital pulse signal 136A has three statesS1, S2, and S3 during an occurrence of a clock cycle of the clocksignal, the digital signal processor DSPA determines whether a logiclevel of the digital pulse signal 136A is 0, 1, or 2. Upon determiningthat the logic level of the digital pulse signal 136A is 1, the digitalsignal processor DSPA identifies an occurrence of the state of thedigital pulse signal 136A to be S1. Similarly, upon determining that thelogic level of the digital pulse signal 136A is 2, the digital signalprocessor DSPA identifies an occurrence of the state of the digitalpulse signal 136A to be S2. Also, upon determining that the logic levelof the digital pulse signal 136A is 0, the digital signal processor DSPAidentifies an occurrence of the state of the digital pulse signal 136Ato be S3.

As yet another example, when the digital pulse signal 136A has twostates S1 and S2 during an occurrence of a clock cycle of the clocksignal, the digital signal processor DSPA determines whether a logiclevel of the digital pulse signal 136A is 0 or 1. Upon determining thatthe logic level of the digital pulse signal 136A is 1, the digitalsignal processor DSPA identifies an occurrence of the state of thedigital pulse signal 136A to be S1. Similarly, upon determining that thelogic level of the digital pulse signal 136A is 0, the digital signalprocessor DSPA identifies an occurrence of the state of the digitalpulse signal 136A to be S2.

Independent of the state of the digital pulse signal 136A, the digitalsignal processor DSPA sends a signal to the frequency controller FCA.Upon receiving the signal from the digital signal processor DSPA, thefrequency controller FCA accesses a frequency level fA stored within thefrequency controller FCA and provides the frequency level fA to thedriver system DRVRA. It should be noted that a frequency level is storedwithin a frequency controller, described herein, within a memory deviceof the frequency controller and the frequency level is accessed by aprocessor of the frequency controller from the memory device of thefrequency controller. Examples of the frequency level fA stored withinthe frequency controller FCA include the low frequency, such as 400 kHzor 2 MHz.

Moreover, in response to identifying the occurrence of the state of thedigital pulse signal 136A to be S1, the digital signal processor DSPAsends a signal to the parameter controller PRAS(n−N). Upon receiving thesignal during the occurrence of the state S1 of the digital pulse signal136A, the parameter controller PRAS(n−N) accesses a parameter levelstored within the parameter controller PRAS(n−N) and provides theparameter level to the driver system DRVRA. An example of the parameterlevel, for the state S1 of the digital pulse signal 136A having the fourstates S1 through S4 during an occurrence of a cycle of the clock signalincludes a parameter level P1 (FIG. 2B). The parameter level P1 isstored within a memory device of the parameter controller PRAS(n−N).Another example of the parameter level, for the state S1 of the digitalpulse signal 136A having the three states S1 through S3 during anoccurrence of a cycle of the clock signal includes a parameter level P2(FIG. 3B). The parameter level P2 is stored within the memory device ofthe parameter controller PRAS(n−N). Yet another example of the parameterlevel, for the state S1 of the digital pulse signal 136A having twostates S1 and S2 during an occurrence of a cycle of the clock signal,includes the parameter level P1 (FIG. 4B).

Similarly, in response to identifying the occurrence of the state of thedigital pulse signal 136A to be S2, the digital signal processor DSPAsends a signal to the parameter controller PRAS(n−2). Upon receiving thesignal during the occurrence of the state S2 of the digital pulse signal136A, the parameter controller PRAS(n−2) accesses a parameter levelstored within the parameter controller PRAS(n−2) and provides theparameter level to the driver system DRVRA. An example of the parameterlevel, for the state S2 of the digital pulse signal 136A having the fourstates S1 through S4 during an occurrence of a cycle of the clock signalincludes the parameter level P2 (FIG. 2B). The parameter level P2 isstored within a memory device of the parameter controller PRAS(n−2).Another example of the parameter level, for the state S2 of the digitalpulse signal 136A having the three states S1 through S3 during anoccurrence of a cycle of the clock signal includes a parameter level P4(FIG. 3B). An example of the parameter level P4 is a power level lessthan 10 watts (W). The parameter level P4 is stored within the memorydevice of the parameter controller PRAS(n−2). Yet another example of theparameter level, for the state S2 of the digital pulse signal 136A,having two states S1 and S2 during an occurrence of a cycle of the clocksignal, includes a parameter level P0 (FIG. 4B). An example of theparameter level P0 is zero power or zero voltage or substantially zeropower or substantially zero voltage. The parameter level P0 is storedwithin the memory device of the parameter controller PRAS(n−2).

Moreover, in response to identifying the occurrence of the state of thedigital pulse signal 136A to be S3, the digital signal processor DSPAsends a signal to the parameter controller PRAS(n−1). Upon receiving thesignal during the occurrence of the state S3 of the digital pulse signal136A, the parameter controller PRAS(n−1) accesses a parameter levelstored within the parameter controller PRAS(n−1) and provides theparameter level to the driver system DRVRA. An example of the parameterlevel, for the state S3 of the digital pulse signal 136A having the fourstates S1 through S4 during an occurrence of a cycle of the clock signalincludes the parameter level P4 (FIG. 2B). The parameter level P4 isstored within a memory device of the parameter controller PRAS(n−1).Another example of the parameter level, for the state S3 of the digitalpulse signal 136A having the three states S1 through S3 during anoccurrence of a cycle of the clock signal, includes a parameter level P0(FIG. 3B). The parameter level P0 is stored within the memory device ofthe parameter controller PRAS (n−1).

Also, in response to identifying the occurrence of the state of thedigital pulse signal 136A to be S4, the digital signal processor DSPAsends a signal to the parameter controller PRAS(n). Upon receiving thesignal during the occurrence of the state S4 of the digital pulse signal136A, the parameter controller PRAS(n) accesses a parameter level storedwithin the parameter controller PRAS(n) and provides the parameter levelto the driver system DRVRA. An example of the parameter level, for thestate S4 of the digital pulse signal 136A having the four states S1through S4 during an occurrence of a cycle of the clock signal, includesthe parameter level P0 (FIG. 2B). The parameter level P4 is storedwithin a memory device of the parameter controller PRAS(n).

During the occurrence of the state S1 of the digital pulse signal 136A,the driver system DRVRA generates a current signal based on thefrequency level fA received from the frequency controller FCA and theparameter level P1 (FIG. 2B), P2 (FIG. 3B), or P1 (FIG. 4B), andprovides the current signal to the RF power supply PSA. Also, the RFpower supply PSA generates the RF signal 102A upon receiving the currentsignal from the driver system DRVRA during the occurrence of the stateS1 of the digital pulse signal 136A. The RF signal 102A has thefrequency level fA and the parameter level P1 (FIG. 2B), P2 (FIG. 3B),or P1 (FIG. 4B) during the occurrence of the state S1 of the digitalpulse signal 136A.

Similarly, during the occurrence of the state S2 of the digital pulsesignal 136A, the driver system DRVRA generates a current signal based onthe frequency level fA received from the frequency controller FCA andthe parameter level P2 (FIG. 2B), P4 (FIG. 3B), or P0 (FIG. 4B), andprovides the current signal to the RF power supply PSA. Also, the RFpower supply PSA generates the RF signal 102A upon receiving the currentsignal from the driver system DRVRA during the occurrence of the stateS2 of the digital pulse signal 136A. The RF signal 102A has thefrequency level fA and the parameter level P2 (FIG. 2B), P4 (FIG. 3B),or P0 (FIG. 4B) during the occurrence of the state S2 of the digitalpulse signal 136A.

Also, during the occurrence of the state S3 of the digital pulse signal136A, the driver system DRVRA generates a current signal based on thefrequency level fA received from the frequency controller FCA and theparameter level P4 (FIG. 2B) or P0 (FIG. 3B), and provides the currentsignal to the RF power supply PSA. Also, the RF power supply PSAgenerates the RF signal 102A upon receiving the current signal from thedriver system DRVRA during the occurrence of the state S3 of the digitalpulse signal 136A. The RF signal 102A has the frequency level fA and theparameter level P4 (FIG. 2B) or P0 (FIG. 3B) during the occurrence ofthe state S3 of the digital pulse signal 136A.

Furthermore, during the occurrence of the state S4 of the digital pulsesignal 136A, the driver system DRVRA generates a current signal based onthe frequency level fA received from the frequency controller FCA andthe parameter level P0 (FIG. 2B), and provides the current signal to theRF power supply PSA. Also, the RF power supply PSA generates the RFsignal 102A upon receiving the current signal from the driver systemDRVRA during the occurrence of the state S4 of the digital pulse signal136A. The RF signal 102A has the frequency level fA and the parameterlevel P0 (FIG. 2B) during the occurrence of the state S4 of the digitalpulse signal 136A.

The processor 124 generates a digital pulse signal 136B and provides thedigital pulse signal 136B to the digital signal processor DSPA. Thedigital pulse signal 136B is synchronized with reference to the clocksignal in a manner described below. The digital pulse signal 136B issupplied via the transfer cable 132B to the digital signal processorDSPB.

Upon receiving the digital pulse signal 136B, the digital signalprocessor DSPB identifies an occurrence of a state of the digital pulsesignal 136B. For example, when the digital pulse signal 136B has threestates S1, S2, and S3 during an occurrence of a clock cycle of the clocksignal, the digital signal processor DSPB determines whether a logiclevel of the digital pulse signal 136B is 0, 1, or 2. Upon determiningthat the logic level of the digital pulse signal 136B is 0, the digitalpulse signal DSPB identifies the occurrence of the state of the digitalpulse signal 136B to be S1. Similarly, upon determining that the logiclevel of the digital pulse signal 136B is 1, the digital pulse signalDSPB identifies the occurrence of the state of the digital pulse signal136B to be S2. Also, upon determining that the logic level of thedigital pulse signal 136B is 2, the digital signal processor DSPBidentifies the occurrence of the state of the digital pulse signal 136Bto be S3.

As another example, when the digital pulse signal 136B has two states S1and S2 during an occurrence of a clock cycle of the clock signal, thedigital signal processor DSPB determines whether a logic level of thedigital pulse signal 136B is 0 or 1. Upon determining that the logiclevel of the digital pulse signal 136B is 0, the digital pulse signalDSPB identifies the occurrence of the state of the digital pulse signal136B to be S1. Similarly, upon determining that the logic level of thedigital pulse signal 136B is 1, the digital pulse signal DSPB identifiesthe occurrence of the state of the digital pulse signal 136B to be S2.

Independent of the state of the digital pulse signal 136B, the digitalsignal processor DSPB sends a signal to the frequency controller FCB.Upon receiving the signal from the digital signal processor DSPB, thefrequency controller FCB accesses a frequency level fB stored within thefrequency controller FCB and provides the frequency level fB to thedriver system DRVRB. Examples of the frequency level fB stored withinthe frequency controller FCB include the high frequency, such as 27 MHzor 60 MHz.

Moreover, in response to identifying the occurrence of the state of thedigital pulse signal 136B to be S1, the digital signal processor DSPBsends a signal to the parameter controller PRBS(n−N). Upon receiving thesignal during the occurrence of the state S1 of the digital pulse signal136B, the parameter controller PRBS(n−N) accesses a parameter levelstored within the parameter controller PRBS(n−N) and provides theparameter level to the driver system DRVRB. An example of the parameterlevel, for the state S1 of the digital pulse signal 136B having thethree states S1 through S3 during an occurrence of a cycle of the clocksignal, includes a parameter level P10 (FIG. 2D). An example of theparameter level P10 is zero power or a zero voltage or substantiallyzero power or substantially zero voltage. The parameter level P10 isstored within a memory device of the parameter controller PRBS(n−N).Another example of the parameter level, for the state S1 of the digitalpulse signal 136B having the two states S1 and S2 during an occurrenceof a cycle of the clock signal includes the parameter level P10 (FIG. 3Dor FIG. 4D).

Similarly, in response to identifying the occurrence of the state of thedigital pulse signal 136B to be S2, the digital signal processor DSPBsends a signal to the parameter controller PRBS(n−2). Upon receiving thesignal during the occurrence of the state S2 of the digital pulse signal136B, the parameter controller PRBS(n−2) accesses a parameter levelstored within the parameter controller PRBS(n−2) and provides theparameter level to the driver system DRVRB. An example of the parameterlevel, for the state S2 of the digital pulse signal 136B having thethree states S1 through S3 during an occurrence of a cycle of the clocksignal includes a parameter level P15 (FIG. 2D). An example of theparameter level P15 is a power level that is greater than or equal to100 watts. The parameter level P15 is stored within a memory device ofthe parameter controller PRBS(n−2). Another example of the parameterlevel, for the state S2 of the digital pulse signal 136A having the twostates S1 and S2 during an occurrence of a cycle of the clock signalincludes the parameter level P15 (FIG. 3D or 4D).

Moreover, in response to identifying the occurrence of the state of thedigital pulse signal 136B to be S3, the digital signal processor DSPBsends a signal to the parameter controller PRBS(n−1). Upon receiving thesignal during the occurrence of the state S3 of the digital pulse signal136B, the parameter controller PRBS(n−1) accesses a parameter levelstored within the parameter controller PRBS(n−1) and provides theparameter level to the driver system DRVRB. An example of the parameterlevel, for the state S3 of the digital pulse signal 136B having thethree states S1 through S3 during an occurrence of a cycle of the clocksignal includes a parameter level P17 (FIG. 2D). The parameter level P17is stored within a memory device of the parameter controller PRBS(n−1).

During the occurrence of the state S1 of the digital pulse signal 136B,the driver system DRVRB generates a current signal based on thefrequency level fB received from the frequency controller FCB and theparameter level P10 (FIG. 2D or 3D or 4D), and provides the currentsignal to the RF power supply PSB. Also, the RF power supply PSBgenerates the RF signal 102B upon receiving the current signal from thedriver system DRVRB during the occurrence of the state S1 of the digitalpulse signal 136B. The RF signal 102B has the frequency level fB and theparameter level P10 (FIG. 2D or 3D or 4D) during the occurrence of thestate S1 of the digital pulse signal 136B.

Similarly, during the occurrence of the state S2 of the digital pulsesignal 136B, the driver system DRVRB generates a current signal based onthe frequency level fB received from the frequency controller FCB andthe parameter level P15 (FIG. 2D or 3D or 4D), and provides the currentsignal to the RF power supply PSB. Also, the RF power supply PSBgenerates the RF signal 102B upon receiving the current signal from thedriver system DRVRB during the occurrence of the state S2 of the digitalpulse signal 136B. The RF signal 102B has the frequency level fB and theparameter level P15 (FIG. 2D or 3D or 4D) during the occurrence of thestate S2 of the digital pulse signal 136B.

Also, during the occurrence of the state S3 of the digital pulse signal136B, the driver system DRVRB generates a current signal based on thefrequency level fB received from the frequency controller FCB and theparameter level P17 (FIG. 2D), and provides the current signal to the RFpower supply PSB. Also, the RF power supply PSB generates the RF signal102B upon receiving the current signal from the driver system DRVRBduring the occurrence of the state S3 of the digital pulse signal 136B.The RF signal 102B has the frequency level fB and the parameter levelP17 (FIG. 2D) during the occurrence of the state S3 of the digital pulsesignal 136B.

The processor 124 generates a digital pulse signal 136C and provides thedigital pulse signal 136C to the digital signal processor DSPC. Thedigital pulse signal 136C is synchronized with reference to the clocksignal in a manner described below. The digital pulse signal 136C issupplied via the transfer cable 132C to the digital signal processorDSPC.

Upon receiving the digital pulse signal 136C, the digital signalprocessor DSPC identifies an occurrence of a state of the digital pulsesignal 136C. For example, when the digital pulse signal 136C has twostates S1 and S2 during an occurrence of a clock cycle of the clocksignal, the digital signal processor DSPC determines whether the logiclevel of the digital pulse signal 136C is 0 or 1. Upon determining thatthe logic level of the digital pulse signal 136C is 0, the digital pulsesignal DSPC identifies the occurrence of the state of the digital pulsesignal 136C to be S1. Similarly, upon determining that the logic levelof the digital pulse signal 136C is 1, the digital pulse signal DSPCidentifies the occurrence of the state of the digital pulse signal 136Cto be S2.

Independent of the state of the digital pulse signal 136C, the digitalsignal processor DSPC sends a signal to the frequency controller FCC.Upon receiving the signal from the digital signal processor DSPC, thefrequency controller FCC accesses a frequency level fC stored within thefrequency controller FCC and provides the frequency level fC to thedriver system DRVRC.

Moreover, in response to identifying the occurrence of the state of thedigital pulse signal 136C to be S1, the digital signal processor DSPCsends a signal to the parameter controller PRCS(n−N). Upon receiving thesignal during the occurrence of the state S1 of the digital pulse signal136C, the parameter controller PRCS(n−N) accesses a parameter levelstored within the parameter controller PRCS(n−N) and provides theparameter level to the driver system DRVRC. An example of the parameterlevel, for the state S1 of the digital pulse signal 136C having the twostates S1 and S2 during an occurrence of a cycle of the clock signal,includes a parameter level P22 (FIG. 2F). The parameter level P22 isstored within a memory device of the parameter controller PRCS(n−N). Anexample of the parameter level P22 is a power level less than or equalto 60 watts.

Similarly, in response to identifying the occurrence of the state of thedigital pulse signal 136C to be S2, the digital signal processor DSPCsends a signal to the parameter controller PRCS(n−2). Upon receiving thesignal during the occurrence of the state S2 of the digital pulse signal136C, the parameter controller PRCS(n−2) accesses a parameter levelstored within the parameter controller PRCS(n−2) and provides theparameter level to the driver system DRVRC. An example of the parameterlevel, for the state S2 of the digital pulse signal 136C having the twostates S1 and S2 during an occurrence of a cycle of the clock signalincludes a parameter level P25 (FIG. 2F). The parameter level P25 isstored within a memory device of the parameter controller PRCS(n−2). Anexample of the parameter level P25 is a power level greater than orequal to 100 watts.

During the occurrence of the state S1 of the digital pulse signal 136C,the driver system DRVRC generates a current signal based on thefrequency level fC received from the frequency controller FCC and theparameter level P22 (FIG. 2F), and provides the current signal to the RFpower supply PSC. Also, the RF power supply PSC generates an RF signal106 upon receiving the current signal from the driver system DRVRCduring the occurrence of the state S1 of the digital pulse signal 136C.The RF signal 106 is sometimes referred to herein as a TCP RF signal.The RF signal 106 has the frequency level fC and the parameter level P22(FIG. 2F) during the occurrence of the state S1 of the digital pulsesignal 136C.

Similarly, during the occurrence of the state S2 of the digital pulsesignal 136C, the driver system DRVRC generates a current signal based onthe frequency level fC received from the frequency controller FCC andthe parameter level P25 (FIG. 2F), and provides the current signal tothe RF power supply PSC. Also, the RF power supply PSC generates the RFsignal 106 upon receiving the current signal from the driver systemDRVRC during the occurrence of the state S2 of the digital pulse signal136C. The RF signal 106 has the frequency level fC and the parameterlevel P25 (FIG. 2F) during the occurrence of the state S2 of the digitalpulse signal 136C.

The impedance match 104 receives the RF signal 102A from the RF powersupply PSA via the RF cable 118A and receives the RF signal 102B fromthe RF power supply PSB via the RF cable 118B, and matches an impedanceof the load coupled to the output O1 with an impedance of the sourcecoupled to the inputs I1 and I2 to generate a modified RF signal 110 atthe output O2. The modified RF signal 110 output from the impedancematch 104 is supplied via the RF transmission line 116 to the substratesupport 128.

Similarly, the impedance match 108 receives the RF signal 106 via the RFcable 122 and matches an impedance of the load coupled to the output ofthe impedance match 108 with an impedance of the source coupled to theinput of the impedance match 108 to generate a modified RF signal 113.The modified RF signal 113 is supplied from the output of the impedancematch 108 to the TCP coil 134.

When one or more process gases are supplied to the plasma chamber 114 inaddition to supplying the modified RF signal 110 and the modified RFsignal 113, plasma is stricken or maintained within the plasma chamber114 to process the substrate S. Examples of the one or more processgases include an oxygen-containing gas, such as O₂. Other examples ofthe one or more process gases include a chlorine-containing gas and afluorine-containing gas, e.g., tetrafluoromethane (CF₄), sulfurhexafluoride (SF₆), hexafluoroethane (C₂F₆), etc. Examples of processingthe substrate S includes depositing a material on the substrate S,etching the substrate S, cleaning the substrate S, and sputtering thesubstrate S.

In one embodiment, the any number of TCP coils, such as two, three, orfour, are disposed above the dielectric window 130. In an embodiment,one or more TCP coils are located next to a sidewall of the plasmachamber 114.

In an embodiment, instead of the plasma chamber 114 being a TCP plasmachamber, a capacitively coupled plasma (CCP) chamber is used. The CCPchamber includes an upper electrode, such as a capacitive plate, and thechuck. The chuck faces the upper electrode. The upper electrode iscoupled to the RF transmission line 120. The upper electrode is made ofa metal, such as aluminum or an alloy of aluminum.

In an embodiment, the parameter controllers PRAS(n−N) through PRAS(n),the frequency controller FCA, and the digital signal processor DSPA areparts of a controller of the RF generator RFGA. For example, functions,described herein, as performed by the parameter controllers PRAS(n−N)through PRAS(n), the frequency controller FCA, and the digital signalprocessor DSPA are performed by the controller of the RF generator RFGA.Similarly, in one embodiment, the parameter controllers PRBS(n−N)through PRBS(n), the frequency controller FCB, and the digital signalprocessor DSPB are parts of a controller of the RF generator RFGB. Also,in a similar manner, in one embodiment, the parameter controllersPRCS(n−N) through PRCS(n), the frequency controller FCC, and the digitalsignal processor DSPC are parts of a controller of the RF generatorRFGC.

In an embodiment, the TCP coil 134 is considered to be a part of theplasma chamber 114.

In one embodiment, a combination of the digital signal processor DSPA,the parameter controllers PRAS(n−N) through PRAS(n), and the frequencycontroller FCA is sometimes referred to herein as a controller. Forexample, each of the digital signal processor DSPA, the parametercontroller PRAS(n−N), the parameter controller PRAS(n−1), the parametercontroller PRAS(n), the frequency controller FCA is a portion, such as ahardware circuit or a software module, of the controller. Similarly, inan embodiment, a combination of the digital signal processor DSPB, theparameter controllers PRBS(n−N) through PRBS(n), and the frequencycontroller FCB is sometimes referred to herein as a controller. Also, inone embodiment, a combination of the digital signal processor DSPC, theparameter controllers PRCS(n−N) through PRCS(n), and the frequencycontroller FCC is sometimes referred to herein as a controller.

In an embodiment, any parameter levels, described herein, of the RFsignal 102A are provided from the processor 124 via the transfer cable132A or another transfer cable to the digital signal processor DSPA. Insome embodiments, the frequency level fA of the RF signal 102A isprovided from the processor 124 via the transfer cable 132A or anothertransfer cable to the digital signal processor DSPA. Upon receiving thefrequency level fA, the digital signal processor DSPA sends thefrequency level to the frequency controller FCA. The parameter levelsand the frequency level fA of the RF signal 102A are stored in thememory device 126.

In one embodiment, any parameter levels, described herein, of the RFsignal 102B are provided from the processor 124 via the transfer cable132B or another transfer cable to the digital signal processor DSPB. Insome embodiments, the frequency level fA of the RF signal 102B isprovided from the processor 124 via the transfer cable 132B or anothertransfer cable to the digital signal processor DSPB. Upon receiving thefrequency level fB, the digital signal processor DSPB sends thefrequency level to the frequency controller FCB. The parameter levelsand the frequency level fB of the RF signal 102B are stored in thememory device 126.

In an embodiment, any parameter levels, described herein, of the RFsignal 106 are provided from the processor 124 via the transfer cable132C or another transfer cable to the digital signal processor DSPC. Insome embodiments, the frequency level fC of the RF signal 106 isprovided from the processor 124 via the transfer cable 132C or anothertransfer cable to the digital signal processor DSPC. Upon receiving thefrequency level fC, the digital signal processor DSPC sends thefrequency level to the frequency controller FCC. The parameter levelsand the frequency level fC of the RF signal 106 are stored in the memorydevice 126.

FIG. 2A is an embodiment of a graph 202 to illustrate a logic level of adigital pulse signal 204 versus time t. The digital pulse signal 204 isan example of the digital pulse signal 136A (FIG. 1) that is provided bythe processor 124 (FIG. 1) to the RF generator RFGA (FIG. 1). During atime period between a time t0 and a time t1, the digital pulse signal204 has an occurrence of the state S1. The state S1 of the digital pulsesignal 204 has the logic level 1. Moreover, during a time period betweenthe time t1 and a time t2, the digital pulse signal 204 has anoccurrence of a state S2, which has the logic level 2. Also, during atime period between the time t2 and a time t3, the digital pulse signal204 has an occurrence of a state S3, which has the logic level 3. Duringa time period between the time t3 and a time t5, the digital pulsesignal 204 has an occurrence of a state S4, which has the logic level 0.The occurrences of the states S1 through S4 of the digital pulse signal204 repeat after the time t5 for a time period between the time t5 and atime t10, and repeat again for a time period after the time t10.

It should be noted that the logic level 1 is greater than the logiclevel 0, the logic level 2 is greater than the logic level 1, and thelogic level 3 is greater than the logic level 2. It should further benoted that any two time periods of the time t are equal. For example,the time period between the times t1 and t2 is equal to the time periodbetween the times t2 and t3 and to the time period between the times t1and t0.

In one embodiment, the digital pulse signal 204 has a duty cycle that isgreater than or equal to 80%. For example, the digital pulse signal 204has a duty cycle that is 80% or substantially 80%, such as a duty cyclewithin 5-10% from the 80% duty cycle. To illustrate, a time periodbetween the times t0 and t3 during which the digital pulse signal 204has the logic level of greater than zero is greater than or equal to 80%of a time period between the times t0 and t5. As another illustration,the digital pulse signal 204 has a duty cycle that can range from 70% to90%.

FIG. 2B is a diagram of an embodiment of a graph 206 to illustrate an RFsignal 208 that is generated by the RF power supply PSA of the RFgenerator RFGA (FIG. 1). The RF signal 208 has the same duty cycle asthat of the digital pulse signal 204 (FIG. 2A). The graph 206 plots aparameter level, such as an amplitude, of the RF signal 208 versus thetime t. The RF signal 208 is an example of the RF signal 102A (FIG. 1)that is generated by the RF generator RFGA. Examples of an amplitude, asused herein, include a peak-to-peak amplitude, a maximum amplitude, anda zero-to-peak amplitude. The RF signal 208 has an occurrence of thestate S1 during the time period between the times t0 and t1. The stateS1 of the RF signal 208 has the parameter level P1. Moreover, the RFsignal 208 has an occurrence of the state S2 during the time periodbetween the times t1 and t2. The state S2 of the RF signal 208 has theparameter level P2. Also, the RF signal 208 has an occurrence of thestate S3 during the time period between the times t2 and t3. The stateS3 of the RF signal 208 has the parameter level P4. The RF signal 208has an occurrence of the state S4 during the time period between thetimes t3 and t5. The state S4 of the RF signal 208 has the parameterlevel P0. Examples of the parameter level P0 include a voltage level ofzero and a power level of zero. Additional examples of the parameterlevel P0 include a voltage level that is substantially zero and a powerlevel that is substantially zero. An example of a voltage level that issubstantially zero is a voltage level that is within 5-10% from avoltage level of zero and an example of a power level that issubstantially zero is a power level that is within 5-10% from a powerlevel of zero. The RF signal 208 has additional occurrences of thestates S1 through S4. Occurrences of the states S1 through S4 of the RFsignal 208 repeat during the time period between the times t5 and t10and again repeat after the time t10.

The state S1 of the RF signal 208 is sometimes referred to herein as alow state, the state S2 of the RF signal 208 is sometimes referred toherein as a medium state, and the state S3 of the RF signal 208 issometimes referred to herein as a high state. The state S4 of the RFsignal 208 is sometimes referred to herein as an off state.

It should be noted that the parameter level P1 is greater than theparameter level P0. The parameter level P2 is greater than the parameterlevel P1 and a parameter level P3 is greater than the parameter levelP2. The parameter level P4 is greater than the parameter level P3.

The RF signal 208 pulses from the state S1 to the state S2 and from thestate S2 to the state S3. For example, the RF signal 208 transitionsfrom the state S1 to the state S2 at the time t1 or substantially at thetime t1 and transitions from the state S2 to the state S3 at the time t2or substantially at the time t2. The RF signal 208 further pulses fromthe state S3 to the state S4. As an example, the RF signal 208transitions from the state S3 to the state S4 at the time t3 orsubstantially at the time t3. The RF signal 208 transitions from thestate S4 to another occurrence of the state S1 at the time t5 orsubstantially at the time t5. As an example, a transition that occurssubstantially at a time is a transition that occurs within 5-10% of theclock cycle from the time. To illustrate, the transition from the stateS2 to the state S3 occurs substantially within 5-10% of a time period ofthe clock cycle from the time t2.

In one embodiment, the state S3 of the RF signal 208 has the parameterlevel P3.

In one embodiment, the memory device 126 stores the parameter levels,described herein, for the RF generator RFGA. The processor 124 providesthe parameter levels to the RF generator RFGA. For example, theprocessor 124 sends the parameter levels of the RF signal 208 and aninstruction via the transfer cable 132A to the digital signal processorDSPA. The parameter levels of the RF signal 208 are stored in the memorydevice 126. The DSPA determines from the instruction to distribute theparameter levels of the RF signal 208 to the parameter controllersPRAS(n−N), PRAS(n−2), PRAS(n−1), and PRAS(n). For example, the parameterlevel P1 is sent from the digital signal processor DSPA to the parametercontroller PRAS(n−N), the parameter level P2 is sent from the digitalsignal processor DSPA to the parameter controller PRAS(n−2), theparameter level P4 is sent from the digital signal processor DSPA to theparameter controller PRAS(n−1), and the parameter level P0 is sent fromthe digital signal processor DSPA to the parameter controller PRAS(n−N).The parameter level P1 is stored in the memory device of the parametercontroller PRAS(n−N), the parameter level P2 is stored in the memorydevice of the parameter controller PRAS(n−2), the parameter level P4 isstored in the memory device of the parameter controller PRAS(n−1), andthe parameter level P0 is stored in the memory device of the parametercontroller PRAS(n).

FIG. 2C is an embodiment of a graph 210 to illustrate a logic level of adigital pulse signal 212 versus the time t. The digital pulse signal 212is an example of the digital pulse signal 136B (FIG. 1) that is providedby the processor 124 (FIG. 1) to the RF generator RFGB (FIG. 1). Duringthe time period between the times t0 and t3, the digital pulse signal212 has an occurrence of the state S1. The state S1 of the digital pulsesignal 212 has the logic level 0. Moreover, during a time period betweenthe time t3 and a time t4, the digital pulse signal 212 has anoccurrence of a state S2, which has the logic level 1. Also, during atime period between the time t4 and the time t5, the digital pulsesignal 212 has an occurrence of a state S3, which has a logic level 2.The occurrences of the states S1 through S3 of the digital pulse signal212 repeat after the time t5 for the time period between the time t5 anda time t10, and repeat again for the time period after the time t10.

In one embodiment, the digital pulse signal 212 has a duty cycle that isless than or equal to 20%. For example, the digital pulse signal 212 hasa duty cycle that is 20% or substantially 20%, such as a duty cyclewithin 5-10% from the 20% duty cycle. To illustrate, a time periodbetween the times t3 and t5 during which the digital pulse signal 212has the logic level of greater than zero is less than or equal to 20% ofa time period between the times t0 and t5. As another illustration, thedigital pulse signal 212 has a duty cycle that can range from 10% to30%.

FIG. 2D is a diagram of an embodiment of a graph 214 to illustrate an RFsignal 216 that is generated by the RF power supply PSB of the RFgenerator RFGB (FIG. 1). A duty cycle of the RF signal 216 is the sameas the duty cycle of the digital pulse signal 212. The graph 214 plots aparameter level, such as an amplitude, of the RF signal 216 versus thetime t. The RF signal 216 is an example of the RF signal 102B (FIG. 1)that is generated by the RF generator RFGB. The RF signal 216 has anoccurrence of the state S1 during the time period between the times t0and t3. The state S1 of the RF signal 216 has a parameter level P10.Examples of the parameter level P10 include a voltage level of zero anda power level of zero. Additional examples of the parameter level P10include a voltage level that is substantially zero and a power levelthat is substantially zero. Moreover, the RF signal 216 has anoccurrence of the state S2 during the time period between the times t3and t4. The state S2 of the RF signal 216 has the parameter level P15.Also, the RF signal 216 has an occurrence of the state S3 during thetime period between the times t4 and t5. The state S3 of the RF signal216 has the parameter level P17. The RF signal 216 has additionaloccurrences of the states S1 through S3. The states S1 through S3 of theRF signal 216 repeat during the time period between the times t5 and t10and again repeat after the time t10.

The state S1 of the RF signal 216 is sometimes referred to herein as anoff state, the state S2 of the RF signal 216 is sometimes referred toherein as a low state, and the state S3 of the RF signal 216 issometimes referred to herein as a high state. A parameter level P11 isgreater than the parameter level P10. A parameter level P12 is greaterthan the parameter level P11 and a parameter level P13 is greater thanthe parameter level P12. A parameter level P14 is greater than theparameter level P13, the parameter level P15 is greater than theparameter level P14, a parameter level P16 is greater than the parameterlevel P15, and the parameter level P17 is greater than the parameterlevel P16. Also, the parameter level P15 is greater than the parameterlevel P4 of the graph 206 of FIG. 2B.

The RF signal 216 pulses from the state S1 to the state S2 and from thestate S2 to the state S3. For example, the RF signal 216 transitionsfrom the state S1 to the state S2 at the time t3 or substantially at thetime t3 and transitions from the state S2 to the state S3 at the time t4or substantially at the time t4. The RF signal 216 further pulses fromthe state S3 to the state S1. As an example, the RF signal 216transitions from the state S3 to another occurrence of the state S1 atthe time t5 or substantially at the time t5.

In one embodiment, the memory device 126 stores the parameter levels,described herein, for the RF generator RFGB. The processor 124 providesthe parameter levels to the RF generator RFGB. For example, theprocessor 124 sends the parameter levels of the RF signal 216 and aninstruction via the transfer cable 132B to the digital signal processorDSPB. The parameter levels of the RF signal 216 are stored in the memorydevice 126. The DSPB determines from the instruction to distribute theparameter levels of the RF signal 216 to the parameter controllersPRBS(n−N), PRBS(n−2), and PRBS(n−1). For example, the parameter levelP10 is sent from the digital signal processor DSPB to the parametercontroller PRBS(n−N), the parameter level P15 is sent from the digitalsignal processor DSPB to the parameter controller PRBS(n−2), and theparameter level P17 is sent from the digital signal processor DSPB tothe parameter controller PRBS(n−1). The parameter level P10 is stored inthe memory device of the parameter controller PRBS(n−N), the parameterlevel P15 is stored in the memory device of the parameter controllerPRBS(n−2), and the parameter level P17 is stored in the memory device ofthe parameter controller PRBS(n−1).

FIG. 2E is an embodiment of a graph 218 to illustrate a logic level of adigital pulse signal 220 versus the time t. The digital pulse signal 220is an example of the digital pulse signal 136C (FIG. 1) that is providedby the processor 124 (FIG. 1) to the RF generator RFGC (FIG. 1). Duringthe time period between the times t0 and t3, the digital pulse signal220 has an occurrence of the state S1. The state S1 of the digital pulsesignal 220 has the logic level 0. Moreover, during a time period betweenthe time t3 and the time t5, the digital pulse signal 220 has anoccurrence of the state S2, which has the logic level 1. The occurrencesof the states S1 and S2 of the digital pulse signal 220 repeat after thetime t5 for the time period between the time t5 and a time t10, andrepeat again for the time period after the time t10.

In one embodiment, the digital pulse signal 220 has a duty cycle that isless than or equal to 20%. For example, the digital pulse signal 220 hasa duty cycle that is 20% or substantially 20%, such as a duty cyclewithin 5-10% from the 20% duty cycle. To illustrate, a time periodbetween the times t3 and t5 during which the digital pulse signal 220has the logic level of greater than zero is less than or equal to 20% ofa time period between the times t0 and t5. As another illustration, thedigital pulse signal 220 has a duty cycle that can range from 10% to30%.

FIG. 2F is a diagram of an embodiment of a graph 222 to illustrate an RFsignal 224 that is generated by the RF power supply PSC of the RFgenerator RFGC (FIG. 1). The graph 222 plots a parameter level, such asan amplitude, of the RF signal 224 versus the time t. The RF signal 224is an example of the RF signal 106 (FIG. 1) that is generated by the RFgenerator RFGC. The RF signal 224 has an occurrence of the state S1during the time period between the times t0 and t3. The state S1 of theRF signal 224 has the parameter level P22. Moreover, the RF signal 224has an occurrence of the state S2 during the time period between thetimes t3 and t5. The state S2 of the RF signal 224 has a parameter levelP25. The RF signal 224 has additional occurrences of the states S1 andS2. The states S1 and S2 of the RF signal 224 repeat during the timeperiod between the times t5 and t10 and again repeat after the time t10.

The state S1 of the RF signal 224 is sometimes referred to herein as alow TCP state and the state S2 of the RF signal 224 is sometimesreferred to herein as a high TCP state. As an example, a duty cycle ofthe low TCP state is greater than or equal to 80% and a duty cycle ofthe high TCP state is less than equal to 20%. A parameter level P21 isgreater than a parameter level P20, which is zero or substantially zero.The parameter level P22 is greater than the parameter level P21 and aparameter level P23 is greater than the parameter level P22. A parameterlevel P24 is greater than the parameter level P23 and the parameterlevel P25 is greater than the parameter level P24.

The RF signal 224 pulses from the state S1 to the state S2 and from thestate S2 to the state S1. For example, the RF signal 224 transitionsfrom the state S1 to the state S2 at the time t3 or substantially at thetime t3 and transitions from the state S2 to the state S1 at the time t5or substantially at the time t5.

As shown from FIGS. 2B, 2D, and 2F, during the low TCP state, the RFsignal 208 is supplied by the RF generator RFGA to the impedance match104 and during the high TCP state, the RF signal 216 is supplied by theRF generator RFGB to the impedance match 104. During the high TCP state,the RF signal 208 is not supplied by the RF generator RFGA and duringthe low TCP state, the RF signal 216 is not supplied by the RF generatorRFGB.

In one embodiment, the parameter level P20 is the same as the parameterlevel P0 (FIG. 2B), the parameter level P21 is the same as the parameterlevel P1 (FIG. 2B), the parameter level P22 is the same as the parameterlevel P2 (FIG. 2B), the parameter level P23 is the same as the parameterlevel P3 (FIG. 2B), the parameter level P24 is the same as the parameterlevel P4 (FIG. 2B), and the parameter level P25 is the same as aparameter level P5 (FIG. 2B).

In an embodiment, the parameter level P20 is the same as the parameterlevel P10 (FIG. 2D), the parameter level P21 is the same as theparameter level P11 (FIG. 2D), the parameter level P22 is the same asthe parameter level P12 (FIG. 2D), the parameter level P23 is the sameas the parameter level P13 (FIG. 2D), the parameter level P24 is thesame as the parameter level P14 (FIG. 2D), and the parameter level P25is the same as the parameter level P15 (FIG. 2D).

In one embodiment, the parameter level P22 is greater than the parameterlevel P15 or P17.

In an embodiment, the parameter level P22 is greater than the parameterlevel P4.

In one embodiment, the memory device 126 stores the parameter levels,described herein, for the RF generator RFGC. The processor 124 providesthe parameter levels to the RF generator RFGC. For example, theprocessor 124 sends the parameter levels of the RF signal 224 and aninstruction via the transfer cable 132C to the digital signal processorDSPC. The parameter levels of the RF signal 224 are stored in the memorydevice 126. The DSPC determines from the instruction to distribute theparameter levels of the RF signal 224 to the parameter controllersPRCS(n−N) and PRCS(n−2). For example, the parameter level P22 is sentfrom the digital signal processor DSPC to the parameter controllerPRCS(n−N) and the parameter level P25 is sent from the digital signalprocessor DSPC to the parameter controller PRCS(n−2). The parameterlevel P22 is stored in the memory device of the parameter controllerPRCS(n−N) and the parameter level P25 is stored in the memory device ofthe parameter controller PRCS(n−2).

FIG. 2G is an embodiment of a graph 226 to illustrate a clock signal 228versus the time t. The clock signal 228 is an example of the clocksignal described above. The clock signal 228 has the logic level 0 for atime period between the time t0 and a time t2.5 and has the logic level1 for a time period between the time t2.5 and the time t5. The time t2.5is in the middle of a time period between the times t2 and t3. The clocksignal 228 transitions from the logic level 0 to the logic level 1 atthe time t2.5 and transitions from the logic level 1 to the logic level0 at the time t5.

The clock signal 228 has multiple clock cycles 1, 2, 3, and so on.During the clock cycle 1, an occurrence of one or more states of an RFsignal or a digital pulse signal, described herein, takes place. Duringthe clock cycle 2, another occurrence of each of the one or more statestakes place and during the clock cycle 3, yet another occurrence of eachof the one or more states takes place.

It should be noted all digital pulse signals, described herein, and allRF signals, described herein, are synchronized to the clock signal 228.For example, the digital pulse signal 204 (FIG. 2A) transitions from thestate S4 to the state S1 at the time t0 at which the clock signal 228transitions from the logic level 1 to the logic level 0. Also, thedigital pulse signal 204 transitions from the state S4 to the state S1at the time t5 at which the clock signal 228 transitions from the logiclevel 1 to the logic level 0. As another example, the RF signal 208(FIG. 2B) transitions from the state S4 to the state S1 at the time t0or substantially at the time t0. Moreover, the RF signal 208 transitionsfrom the state S4 to the state S1 at the time t5 or substantially at thetime t5. As yet another example, the digital pulse signal 212 (FIG. 2C)transitions from the state S3 to the state S1 at the time t0 andtransitions from the state S3 to the state S1 at the time t5. Also, asanother example, the RF signal 216 (FIG. 2D) transitions from the stateS3 to the state S1 at the time t0 or substantially at the time t0. Also,the RF signal 216 transitions from the state S3 to the state S1 at thetime t5 or substantially at the time t5. As another example, the digitalpulse signal 220 (FIG. 2E) transitions from the state S2 to the state S1at the time t0 and at the time t5. As yet another example, the RF signal224 transitions from the state S2 to the state S1 at the time t0 orsubstantially at the time t0. The RF signal 224 transitions from thestate S2 to the state S1 at the time t5 or substantially at the time t5.

FIG. 3A is an embodiment of a graph 302 to illustrate a logic level of adigital pulse signal 304 versus the time t. The digital pulse signal 304is an example of the digital pulse signal 136A (FIG. 1) that is providedby the processor 124 (FIG. 1) to the RF generator RFGA (FIG. 1). Duringa time period between a time t0 and a time t1.5, the digital pulsesignal 304 has an occurrence of a state S1. The time t1.5 occurs in themiddle of a time period between the time t0 and the time t2. Forexample, the time t1.5 splits the time period from the time t0 to thetime t2 into two halves. The state S1 of the digital pulse signal 304has the logic level 1. Moreover, during a time period between the timet1.5 and the time t3, the digital pulse signal 304 has an occurrence ofa state S2, which has the logic level 2. Also, during a time periodbetween the time t3 and the time t5, the digital pulse signal 304 has anoccurrence of a state S3, which has the logic level 0. The occurrencesof the states S1 through S3 of the digital pulse signal 304 repeat afterthe time t5 for a time period between the time t5 and a time t10, andrepeat again for a time period after the time t10.

In one embodiment, the digital pulse signal 304 has a duty cycle that isgreater than or equal to 80%. For example, the digital pulse signal 304has a duty cycle that is 80% or substantially 80%, such as a duty cyclewithin 5-10% from the 80% duty cycle. To illustrate, a time periodbetween the times t0 and t3 during which the digital pulse signal 304has the logic level of greater than zero is greater than or equal to 80%of a time period between the times t0 and t5. As another illustration,the digital pulse signal 304 has a duty cycle that can range from 70% to90%.

FIG. 3B is a diagram of an embodiment of a graph 306 to illustrate an RFsignal 308 that is generated by the RF power supply PSA of the RFgenerator RFGA (FIG. 1). The RF signal 308 has the same duty cycle asthat of the digital pulse signal 304 (FIG. 3A). The graph 306 plots aparameter level, such as an amplitude, of the RF signal 308 versus thetime t. The RF signal 308 is an example of the RF signal 102A (FIG. 1)that is generated by the RF generator RFGA. The RF signal 308 has anoccurrence of the state S1 during the time period between the times t0and t1.5. The state S1 of the RF signal 308 has the parameter level P2.Moreover, the RF signal 308 has an occurrence of the state S2 during thetime period between the times t1.5 and t3. The state S2 of the RF signal308 has the parameter level P4. Also, the RF signal 308 has anoccurrence of the state S3 during the time period between the times t3and t5. The state S3 of the RF signal 308 has the parameter level P0.Occurrences of the states S1 through S3 of the RF signal 308 repeatduring the time period between the times t5 and t10 and again repeatafter the time t10.

The state S1 of the RF signal 308 is sometimes referred to herein as alow state, the state S2 of the RF signal 308 is sometimes referred toherein as a high state, and the state S3 of the RF signal 308 issometimes referred to herein as an off state.

The RF signal 308 pulses from the state S1 to the state S2 and from thestate S2 to the state S3. For example, the RF signal 308 transitionsfrom the state S1 to the state S2 at the time t1.5 or substantially atthe time t1.5 and transitions from the state S2 to the state S3 at thetime t3 or substantially at the time t3. The RF signal 308 transitionsfrom the state S3 to another occurrence of the state S1 at the time t5or substantially at the time t5.

In one embodiment, the state S1 of the RF signal 308 has the parameterlevel P1 and the state S2 of the RF signal 308 has the parameter levelP2 or P3 or P4.

In one embodiment, the memory device 126 stores the parameter levels,described herein, for the RF generator RFGA. The processor 124 providesthe parameter levels to the RF generator RFGA. For example, theprocessor 124 sends the parameter levels of the RF signal 308 and aninstruction via the transfer cable 132A to the digital signal processorDSPA. The parameter levels of the RF signal 308 are stored in the memorydevice 126. The DSPA determines from the instruction to distribute theparameter levels of the RF signal 308 to the parameter controllersPRAS(n−N), PRAS(n−2), and PRAS(n−1). For example, the parameter level P2is sent from the digital signal processor DSPA to the parametercontroller PRAS(n−N), the parameter level P4 is sent from the digitalsignal processor DSPA to the parameter controller PRAS(n−2), and theparameter level P0 is sent from the digital signal processor DSPA to theparameter controller PRAS(n−1). The parameter level P2 is stored in thememory device of the parameter controller PRAS(n−N), the parameter levelP4 is stored in the memory device of the parameter controller PRAS(n−2),and the parameter level P0 is stored in the memory device of theparameter controller PRAS(n−1).

FIG. 3C is an embodiment of a graph 310 to illustrate a logic level of adigital pulse signal 312 versus the time t. The digital pulse signal 312is an example of the digital pulse signal 136B (FIG. 1) that is providedby the processor 124 (FIG. 1) to the RF generator RFGB (FIG. 1). Duringthe time period between the times t0 and t3, the digital pulse signal312 has an occurrence of a state S1. The state S1 of the digital pulsesignal 312 has the logic level 0. Moreover, during a time period betweenthe time t3 and the time t5, the digital pulse signal 312 has anoccurrence of a state S2, which has the logic level 1. The occurrencesof the states S1 and S2 of the digital pulse signal 312 repeat after thetime t5 for the time period between the time t5 and a time t10, andrepeat again for the time period after the time t10.

In one embodiment, the digital pulse signal 312 has a duty cycle that isless than or equal to 20%. For example, the digital pulse signal 312 hasa duty cycle that is 20% or substantially 20%, such as a duty cyclewithin 5-10% from the 20% duty cycle. To illustrate, a time periodbetween the times t3 and t5 during which the digital pulse signal 312has the logic level of greater than zero is less than or equal to 20% ofa time period between the times t0 and t5. As another illustration, thedigital pulse signal 312 has a duty cycle that can range from 10% to30%.

FIG. 3D is a diagram of an embodiment of a graph 314 to illustrate an RFsignal 316 that is generated by the RF power supply PSB of the RFgenerator RFGB (FIG. 1). A duty cycle of the RF signal 316 is the sameas the duty cycle of the digital pulse signal 312. The graph 314 plots aparameter level, such as an amplitude, of the RF signal 316 versus thetime t. The RF signal 316 is an example of the RF signal 102B (FIG. 1)that is generated by the RF generator RFGB. The RF signal 316 has anoccurrence of the state S1 during the time period between the times t0and t3. The state S1 of the RF signal 216 has the parameter level P10.Moreover, the RF signal 316 has an occurrence of the state S2 during thetime period between the times t3 and t5. The state S2 of the RF signal316 has the parameter level P15. The RF signal 316 has additionaloccurrences of the states S1 and S2. The states S1 and S2 of the RFsignal 316 repeat during the time period between the times t5 and t10and again repeat after the time t10.

The state S1 of the RF signal 316 is sometimes referred to herein as anoff state, the state S2 of the RF signal 316 is sometimes referred toherein as an on state.

The RF signal 316 pulses from the state S1 to the state S2 and from thestate S2 to the state S1. For example, the RF signal 316 transitionsfrom the state S1 to the state S2 at the time t3 or substantially at thetime t3 and transitions from the state S2 to the state S1 at the time t5or substantially at the time t5.

It should be noted that the RF signal 224 is supplied by the RFgenerator RFGC to the impedance match 108 (FIG. 1) simultaneous with thesupply of the RF signal 308 from the RF generator RFGA to the impedancematch 104 (FIG. 1) and the supply of the RF signal 316 from the RFgenerator RFGB to the impedance match 104. For example, the RF signal308 is supplied by the RF generator RFGA to the impedance match 104 andthe RF signal 316 is supplied by the RF generator RFGB to the impedancematch 104 during the one or more clock cycles of the clock signal 228(FIG. 2G). Also, the RF signal 224 is supplied by the RF generator RFGCto the impedance match 108 during the same one or more clock cycles ofthe clock signal 228.

As shown from FIGS. 3B, 3D, and 2F, during the low TCP state, the RFsignal 308 is supplied by the RF generator RFGA to the impedance match104 and during the high TCP state, the RF signal 316 is supplied by theRF generator RFGB to the impedance match 104. During the high TCP state,the RF signal 308 is not supplied by the RF generator RFGA and duringthe low TCP state, the RF signal 316 is not supplied by the RF generatorRFGB.

In one embodiment, the memory device 126 stores the parameter levels,described herein, for the RF generator RFGB. The processor 124 providesthe parameter levels to the RF generator RFGB. For example, theprocessor 124 sends the parameter levels of the RF signal 316 and aninstruction via the transfer cable 132B to the digital signal processorDSPB. The parameter levels of the RF signal 316 are stored in the memorydevice 126. The DSPB determines from the instruction to distribute theparameter levels of the RF signal 316 to the parameter controllersPRBS(n−N) and PRBS(n−2). For example, the parameter level P10 is sentfrom the digital signal processor DSPB to the parameter controllerPRBS(n−N) and the parameter level P15 is sent from the digital signalprocessor DSPB to the parameter controller PRBS(n−2). The parameterlevel P10 is stored in the memory device of the parameter controllerPRBS(n−N) and the parameter level P15 is stored in the memory device ofthe parameter controller PRBS(n−2).

FIG. 4A is an embodiment of a graph 402 to illustrate a logic level of adigital pulse signal 404 versus the time t. The digital pulse signal 404is an example of the digital pulse signal 136A (FIG. 1) that is providedby the processor 124 (FIG. 1) to the RF generator RFGA (FIG. 1). Duringa time period between a time t0 and the time t3, the digital pulsesignal 404 has an occurrence of the state S1. The state S1 of thedigital pulse signal 404 has the logic level 1. Moreover, during a timeperiod between the time t3 and the time t5, the digital pulse signal 404has an occurrence of the state S2, which has the logic level 0. Theoccurrences of the states S1 and S2 of the digital pulse signal 404repeat after the time t5 for a time period between the time t5 and atime t10, and repeat again for a time period after the time t10.

In one embodiment, the digital pulse signal 404 has a duty cycle that isgreater than or equal to 80%. For example, the digital pulse signal 404has a duty cycle that is 80% or substantially 80%, such as a duty cyclewithin 5-10% from the 80% duty cycle. To illustrate, a time periodbetween the times t0 and t3 during which the digital pulse signal 404has the logic level of greater than zero is greater than or equal to 80%of a time period between the times t0 and t5. As another illustration,the digital pulse signal 404 has a duty cycle that ranges from 70% to90%.

FIG. 4B is a diagram of an embodiment of a graph 406 to illustrate an RFsignal 408 that is generated by the RF power supply PSA of the RFgenerator RFGA (FIG. 1). The RF signal 408 has the same duty cycle asthat of the digital pulse signal 404 (FIG. 4A). The graph 406 plots aparameter level, such as an amplitude, of the RF signal 408 versus thetime t. The RF signal 408 is an example of the RF signal 102A (FIG. 1)that is generated by the RF generator RFGA. The RF signal 408 has anoccurrence of a state S1 during the time period between the times t0 andt3. The state S1 of the RF signal 408 has the parameter level P1.Moreover, the RF signal 408 has an occurrence of a state S2 during thetime period between the times t3 and t5. The state S2 of the RF signal408 has the parameter level P0. Occurrences of the states S1 and S2 ofthe RF signal 408 repeat during the time period between the times t5 andt10 and again repeat after the time t10.

The state S1 of the RF signal 408 is sometimes referred to herein as anon state and the state S2 of the RF signal 408 is sometimes referred toherein as an off state.

The RF signal 406 pulses from the state S1 to the state S2 and from thestate S2 to the state S1. For example, the RF signal 408 transitionsfrom the state S1 to the state S2 at the time t3 or substantially at thetime t3 and transitions from the state S2 to the state S1 at the time t5or substantially at the time t5.

In one embodiment, the state S1 of the RF signal 308 has the parameterlevel P2 or P3 or P4.

In one embodiment, the memory device 126 stores the parameter levels,described herein, for the RF generator RFGA. The processor 124 providesthe parameter levels to the RF generator RFGA. For example, theprocessor 124 sends the parameter levels of the RF signal 408 and aninstruction via the transfer cable 132A to the digital signal processorDSPA. The parameter levels of the RF signal 408 are stored in the memorydevice 126. The DSPA determines from the instruction to distribute theparameter levels of the RF signal 408 to the parameter controllersPRAS(n−N) and PRAS(n−2). For example, the parameter level P1 is sentfrom the digital signal processor DSPA to the parameter controllerPRAS(n−N) and the parameter level P0 is sent from the digital signalprocessor DSPA to the parameter controller PRAS(n−2). The parameterlevel P1 is stored in the memory device of the parameter controllerPRAS(n−N) and the parameter level P0 is stored in the memory device ofthe parameter controller PRAS(n−2).

FIG. 4C is an embodiment of the graph 310 to illustrate that the digitalpulse signal 312 is supplied from the processor 124 (FIG. 1) to the RFgenerator RFGB simultaneous with supplying the digital pulse signal 404to the RF generator RFGA.

FIG. 4D is a diagram of an embodiment of the graph 314 to illustratethat the RF signal 316 is supplied by the RF generator RFGB to theimpedance match 104 in synchronization with the digital pulse signal312.

It should be noted that the RF signal 224 is supplied by the RFgenerator RFGC to the impedance match 108 (FIG. 1) simultaneous with thesupply of the RF signal 408 from the RF generator RFGA to the impedancematch 104 (FIG. 1) and the supply of the RF signal 316 from the RFgenerator RFGB to the impedance match 104. For example, the RF signal408 is supplied by the RF generator RFGA to the impedance match 104 andthe RF signal 316 is supplied by the RF generator RFGB to the impedancematch 104 during the one or more clock cycles of the clock signal 228(FIG. 2G). Also, the RF signal 224 is supplied by the RF generator RFGCto the impedance match 108 during the same one or more clock cycles ofthe clock signal 228.

As shown from FIGS. 4B, 4D, and 2F, during the low TCP state, the RFsignal 408 is supplied by the RF generator RFGA to the impedance match104 and during the high TCP state, the RF signal 316 is supplied by theRF generator RFGB to the impedance match 104. During the high TCP state,the RF signal 408 is not supplied by the RF generator RFGA and duringthe low TCP state, the RF signal 316 is not supplied by the RF generatorRFGB.

In one embodiment, the states of the RF signal 102A (FIG. 1) between thetimes t0 and t3 are sometimes referred to herein as a low bias state andthe states of the RF signal 102B (FIG. 1) between the times t3 and t5are sometimes referred to herein as a high bias state.

In an embodiment, an amplitude at a parameter level for a state isoutside a pre-determined range from an amplitude at a differentparameter level for another state. For example, a peak-to-peak magnitudeof the parameter level P2 is greater than a peak-to-peak magnitude ofthe parameter level P1 by at least 15%.

In one embodiment, functions described herein as performed by acontroller, such as a parameter controller or a frequency controller,are performed by a processor of the controller.

FIG. 5 is a diagram to illustrate chemical reactions between a processgas, such as chorine (Cl₂), electrons and ions, which are mostlygenerated during the high TCP state and the high bias state. A moleculeof the process gas Cl₂ is labeled as Cl2 in FIG. 5. The process gas issupplied to a gap between the upper electrode 130 (FIG. 1) and thesubstrate support 128 (FIG. 1).

In a vibrational excitation reaction during the low TCP and low biasstate, the process gas Cl₂ interacts with an electron and the resultingexcited Cl2 molecule can have further successive electron interactions.The electrons are mostly generated during the high TCP state and thehigh bias state but continue to be generated during the low TCP and lowbias state. The processor gas Cl₂ interacts with the electrons and isvibrationally excited. For example, the molecule Cl2 interacts with anelectron e to create a vibrational state v of the molecule Cl2. Theincrease in the vibrational state of the molecule Cl2 is shown asCl2_((v=1)) in FIG. 5. For each electron that vibrationally excites themolecule Cl2, an amount of energy of the molecule Cl2 increases by 0.3electron volts (eV) and the vibration state of the molecule Cl2increases from zero to 1, which is represented as v=1.

In a dissociative attachment reaction that occurs during the low TCP andlow bias state, the process gas Cl2 interacts with the electrons todisassociate into negative ions and atoms. For example, the molecule Cl2interacts with one electron to disassociate into a negative chlorineion, represented by Cl⁻, and a chlorine atom, represented by Cl. Anamount of energy of the negative chlorine ion increases by 0.08 eV.Moreover, in the dissociative attachment reaction, the process gas Cl2with the increased vibration state interacts with one or more otherelectrons to disassociate into negative ions and atoms. As an example,the molecule Cl2 having the vibrational state v=1 interacts with oneelectron to disassociate into a negative chlorine ion, represented byCl⁻, and a chlorine atom, represented by Cl. An amount of energy of thenegative chlorine ion increases by 0.08 eV.

In an ion neutralization reaction that occurs during the low TCP and lowbias state, the negative chlorine ions generated in the low TCP stateand the low bias state interact with positive chlorine ions generatedduring the high TCP state and the high bias state to generate hotneutral atoms. For example, the negative chlorine ion interacts with thepositive chlorine ion, represented as Cl⁺, to generate two hot neutralatoms. Each hot neutral atom is represented as Cl**. Moreover in the ionneutralization reaction, the electrons from the low TCP state and thelow bias state interacts with the positive chlorine ions from the highTCP state and the high bias state to generate hot neutral atoms. Forexample, the electron e interacts with the positive chlorine ion togenerate a hot neutral atom.

Also, in a translational hot atom reaction that occurs during the lowTCP reaction and the low bias state, the electrons from the low TCPstate and the low bias state interact with the chlorine molecules thatare vibrationally excited to generate hot neutral atoms. As an example,the electron e interacts with a vibrationally exited chlorine moleculeCL2 having a vibrational state v=q to generate hot neutral atoms, whereq is a total number of successive electron impacts.

In a charge exchange reaction that occurs during the low TCP state andthe low bias state, the process gas chlorine interacts with chlorinemolecular ions to generate hot neutral molecules. For example, achlorine molecule of the process gas interacts with a chlorine molecularion that is generated by the high TCP and high bias state. Theinteraction generates a hot neutral molecule, represented as Cl2**. Thechlorine molecule Cl2 changes into the hot neutral molecule, representedas Cl2**. It should be noted that a hot neutral molecule or a hotneutral atom or a combination thereof is sometimes referred to herein asa hot neutral. The hot neutral is sometimes referred to herein as a highenergy neutral.

FIG. 6A is an embodiment of an embodiment of a graph 602 to illustrate aplot of energy of hot neutrals versus an angle θ, measured in degrees toillustrate an angular spread of the hot neutrals across a surface of thesubstrate S. The graph 602 is plotted when a continuous bias voltage isapplied to the substrate support 128 (FIG. 1). For example, an RF signal(not shown) that is applied to the substrate support 128 is not pulsedfrom one state to another. As another example, the RF signal (not shown)that is applied to the substrate support 128 has a single parameterlevel. As shown in FIG. 6A, a low number of hot neutrals are created bythe continuous bias voltage.

FIG. 6B is a diagram of an embodiment of a graph 604 to illustrate aplot of hot energy neutrals versus the angle θ. The plot 604 isgenerated when the low TCP state and the low bias state are applied.There is a large amount of hot neutrals generated as a result of thevibrational excitation and the ion neutralization reactions during thelow TCP state and the low bias state. The large amount of hot neutralsare isotropic.

FIG. 6C is a diagram of an embodiment of a graph 606 to illustrate aplot of hot neutrals versus the angle θ. The plot 606 is generated whenthe low TCP state and the low bias state are applied. A directionalityof the hot neutrals increases as a result of the charge exchangereactions during the low TCP state and the low bias state. The increasein the directionality decreases an angular spread of the hot neutralsacross a surface of the substrate S. The directionality of the hotneutrals increases as a result of pulsing of the RF signal 102A duringthe low TCP state. For example, the directionality increases due topulsing of the RF signal 208 (FIG. 2B) from the state S1 to the state S2and further to the state S3. As another example, the directionalityincreases due to pulsing of the RF signal 308 (FIG. 3B) from the stateS1 to the state S2. The hot neutrals have a low angular spread with theincreased directionality. The directionality facilitates etching densefeatures of the substrate S (FIG. 1) and increases an etch rate ofetching the dense features.

In a similar manner, pulsing of the RF signal 102B (FIG. 1) increasesdirectionality of ions of plasma during the high TCP state. For example,the pulsing of the RF signal 216 (FIG. 2D) from the state S2 to thestate S3 increases directionality of ions to reduce an angular spread ofthe ions across the top surface of the substrate S to facilitate anincrease in etch rate of etching the isolation features of the substrateS.

FIG. 7A is a diagram of an embodiment of a substrate 702 to illustratedepths of isolation features and dense features after the high TCP stateand the high bias state. The substrate 702 is an example of thesubstrate S (FIG. 1). The substrate 702 has a silicon layer 704A and asilicon dioxide layer 704B that is overlaid on top of the silicon layer704A. The substrate 702 has multiple isolation features, such as anisolation feature 706A, and has multiple dense features, such as a densefeature 706B. The isolation feature 706A has a wider opening than anopening of the dense feature 706B.

The isolation features are etched at a higher rate during the high TCPstate and the high bias state compared to the dense features. Theisolation features and the dense features are etched by ions generatedin the high TCP state and the high bias state. Due to the wider openingsof the isolation features, the isolation features are etched at thehigher rate. Similarly, due to the narrower openings of the densefeatures, the dense features are etched at a lower rate during the highTCP state and the high bias state. Also, during the high TCP state andthe high bias state, there is a higher amount of passivation by radicalswithin etch depths of the isolation features compared to an amount ofpassivation of the radicals within etch depths of the dense features.The higher amount of passivation creates passivation layers, such as apassivation layer 708, within the etch depths of the isolation features.During the high TCP state and the high bias state, the radicals are ableto enter the wider openings of the isolation features to create thepassivation layers and have difficulty in entering the narrower openingsof the dense features.

FIG. 7B is a diagram of an embodiment of the substrate 702 afterapplying the low TCP state and the low bias state, such as after 30percent of a pre-determined time period T. The hot neutrals generatedduring the low TCP state and the low bias state etch the dense featuresduring the low TCP state and the low bias state and it is difficult forthe hot neutrals to etch the isolation features during the low TCP stateand low bias state. It is difficult for the hot neutrals to etch theisolation features due to the passivation layer 708 (FIG. 7A). The hotneutrals do not have enough energy to quickly etch away the passivationlayer 708. As a result, the dense features are etched at a faster rateduring the low TCP state and the low bias state than the isolationfeatures.

FIG. 7C is a diagram of an embodiment of the substrate 702 afterapplying the low TCP and low bias state, such as after 50 percent of thepre-determined time period T. As shown in FIG. 7C, an etch depth of thedense feature is the same or substantially the same as an etch depth ofthe isolation features.

FIG. 7D is a diagram of an embodiment of the substrate 702 afterapplying the low TCP state and the low bias state, such as after 100percent of the pre-determined time period T. As shown in FIG. 7D, anetch depth of the dense feature 706B is the same or substantially thesame as an etch depth of the isolation feature 706A.

As such, by applying the low TCP state and the low bias state and thehigh TCP state and the high bias state, the dense features and theisolation features are etched by the same amount or substantially thesame amount.

Embodiments described herein may be practiced with various computersystem configurations including hand-held hardware units, microprocessorsystems, microprocessor-based or programmable consumer electronics,minicomputers, mainframe computers and the like. The embodiments canalso be practiced in distributed computing environments where tasks areperformed by remote processing hardware units that are linked through anetwork.

In some embodiments, a controller is part of a system, which may be partof the above-described examples. Such systems include semiconductorprocessing equipment, including a processing tool or tools, chamber orchambers, a platform or platforms for processing, and/or specificprocessing components (a wafer pedestal, a gas flow system, etc.). Thesesystems are integrated with electronics for controlling their operationbefore, during, and after processing of a semiconductor wafer orsubstrate. The electronics is referred to as the “controller,” which maycontrol various components or subparts of the system or systems. Thecontroller, depending on the processing requirements and/or the type ofsystem, is programmed to control any of the processes disclosed herein,including the delivery of process gases, temperature settings (e.g.,heating and/or cooling), pressure settings, vacuum settings, powersettings, RF generator settings, RF matching circuit settings, frequencysettings, flow rate settings, fluid delivery settings, positional andoperation settings, wafer transfers into and out of a tool and othertransfer tools and/or load locks coupled to or interfaced with a system.

Broadly speaking, in a variety of embodiments, the controller is definedas electronics having various integrated circuits, logic, memory, and/orsoftware that receive instructions, issue instructions, controloperation, enable cleaning operations, enable endpoint measurements, andthe like. The integrated circuits include chips in the form of firmwarethat store program instructions, digital signal processors (DSPs), chipsdefined as ASICs, PLDs, and/or one or more microprocessors, ormicrocontrollers that execute program instructions (e.g., software). Theprogram instructions are instructions communicated to the controller inthe form of various individual settings (or program files), defining theparameters, the factors, the variables, etc., for carrying out aparticular process on or for a semiconductor wafer or to a system. Theprogram instructions are, in some embodiments, a part of a recipedefined by process engineers to accomplish one or more processing stepsduring the fabrication of one or more layers, materials, metals, oxides,silicon, silicon dioxide, surfaces, circuits, and/or dies of a wafer.

The controller, in some embodiments, is a part of or coupled to acomputer that is integrated with, coupled to the system, otherwisenetworked to the system, or a combination thereof. For example, thecontroller is in a “cloud” or all or a part of a fab host computersystem, which allows for remote access of the wafer processing. Thecomputer enables remote access to the system to monitor current progressof fabrication operations, examines a history of past fabricationoperations, examines trends or performance metrics from a plurality offabrication operations, to change parameters of current processing, toset processing steps to follow a current processing, or to start a newprocess.

In some embodiments, a remote computer (e.g. a server) provides processrecipes to a system over a network, which includes a local network orthe Internet. The remote computer includes a user interface that enablesentry or programming of parameters and/or settings, which are thencommunicated to the system from the remote computer. In some examples,the controller receives instructions in the form of data, which specifythe parameters, factors, and/or variables for each of the processingsteps to be performed during one or more operations. It should beunderstood that the parameters, factors, and/or variables are specificto the type of process to be performed and the type of tool that thecontroller is configured to interface with or control. Thus as describedabove, the controller is distributed, such as by including one or morediscrete controllers that are networked together and working towards acommon purpose, such as the processes and controls described herein. Anexample of a distributed controller for such purposes includes one ormore integrated circuits on a chamber in communication with one or moreintegrated circuits located remotely (such as at the platform level oras part of a remote computer) that combine to control a process on thechamber.

Without limitation, in various embodiments, example systems to which themethods, described herein, are applied include a plasma etch chamber ormodule, a deposition chamber or module, a spin-rinse chamber or module,a metal plating chamber or module, a clean chamber or module, a beveledge etch chamber or module, a physical vapor deposition (PVD) chamberor module, a chemical vapor deposition (CVD) chamber or module, anatomic layer deposition (ALD) chamber or module, an atomic layer etch(ALE) chamber or module, an ion implantation chamber or module, a trackchamber or module, and any other semiconductor processing systems thatis associated or used in the fabrication and/or manufacturing ofsemiconductor wafers.

It is further noted that in some embodiments, the above-describedoperations apply to several types of plasma chambers, e.g., a plasmachamber including an inductively coupled plasma (ICP) reactor, atransformer coupled plasma chamber, conductor tools, dielectric tools, aplasma chamber including an electron cyclotron resonance (ECR) reactor,etc. For example, one or more RF generators are coupled to an inductorwithin the ICP reactor. Examples of a shape of the inductor include asolenoid, a dome-shaped coil, a flat-shaped coil, etc.

As noted above, depending on the process step or steps to be performedby the tool, the host computer communicates with one or more of othertool circuits or modules, other tool components, cluster tools, othertool interfaces, adjacent tools, neighboring tools, tools locatedthroughout a factory, a main computer, another controller, or tools usedin material transport that bring containers of wafers to and from toollocations and/or load ports in a semiconductor manufacturing factory.

With the above embodiments in mind, it should be understood that some ofthe embodiments employ various computer-implemented operations involvingdata stored in computer systems. These operations are those physicallymanipulating physical quantities. Any of the operations described hereinthat form part of the embodiments are useful machine operations.

Some of the embodiments also relate to a hardware unit or an apparatusfor performing these operations. The apparatus is specially constructedfor a special purpose computer. When defined as a special purposecomputer, the computer performs other processing, program execution orroutines that are not part of the special purpose, while still beingcapable of operating for the special purpose.

In some embodiments, the operations may be processed by a computerselectively activated or configured by one or more computer programsstored in a computer memory, cache, or obtained over the computernetwork. When data is obtained over the computer network, the data maybe processed by other computers on the computer network, e.g., a cloudof computing resources.

One or more embodiments can also be fabricated as computer-readable codeon a non-transitory computer-readable medium. The non-transitorycomputer-readable medium is any data storage hardware unit, e.g., amemory device, etc., that stores data, which is thereafter be read by acomputer system. Examples of the non-transitory computer-readable mediuminclude hard drives, network attached storage (NAS), ROM, RAM, compactdisc-ROMs (CD-ROMs), CD-recordables (CD-Rs), CD-rewritables (CD-RWs),magnetic tapes and other optical and non-optical data storage hardwareunits. In some embodiments, the non-transitory computer-readable mediumincludes a computer-readable tangible medium distributed over anetwork-coupled computer system so that the computer-readable code isstored and executed in a distributed fashion.

Although the method operations above were described in a specific order,it should be understood that in various embodiments, other housekeepingoperations are performed in between operations, or the method operationsare adjusted so that they occur at slightly different times, or aredistributed in a system which allows the occurrence of the methodoperations at various intervals, or are performed in a different orderthan that described above.

It should further be noted that in an embodiment, one or more featuresfrom any embodiment described above are combined with one or morefeatures of any other embodiment without departing from a scopedescribed in various embodiments described in the present disclosure.

Although the foregoing embodiments have been described in some detailfor purposes of clarity of understanding, it will be apparent thatcertain changes and modifications can be practiced within the scope ofappended claims. Accordingly, the present embodiments are to beconsidered as illustrative and not restrictive, and the embodiments arenot to be limited to the details given herein.

What is claimed is:
 1. A system for etching isolation and dense featureswithin a substrate, comprising: a low frequency radio frequency (RF)generator configured to supply a low frequency bias RF signal to a firstimpedance matching circuit; a high frequency RF generator configured tosupply a high frequency bias RF signal to the first impedance matchingcircuit; and a transformer coupled plasma (TCP) RF generator configuredto pulse a TCP RF signal between a low TCP state and a high TCP state toprovide the TCP RF signal to a second impedance matching circuit,wherein the low frequency bias RF signal is supplied during the low TCPstate to etch the dense features and the high frequency bias RF signalis supplied during the high TCP state to etch the isolation features. 2.The system of claim 1, wherein low frequency RF generator is configuredto maintain the low frequency bias RF signal in an off state during thehigh TCP state, and wherein the high frequency RF generator isconfigured to maintain the high frequency bias RF signal in an off stateduring the low TCP state.
 3. The system of claim 1, wherein the firstimpedance matching circuit is configured to output a modified bias RFsignal to a plasma chamber upon receiving the low and high frequencybias RF signals, and wherein the second impedance matching circuit isconfigured to output a modified TCP RF signal to the plasma chamber uponreceiving the TCP RF signal.
 4. The system of claim 1, wherein the lowfrequency RF generator is configured to pulse the low frequency bias RFsignal during the low TCP state, and wherein the high frequency RFgenerator is configured to pulse the high frequency bias RF signalduring the high TCP state.
 5. The system of claim 1, wherein the lowfrequency RF generator is configured to pulse the low frequency bias RFsignal during the low TCP state from a low state to a medium state andfrom the medium state to a high state, and wherein the high frequency RFgenerator is configured to pulse the high frequency bias RF signalduring the high TCP state from a low state to a high state.
 6. Thesystem of claim 5, wherein the low frequency RF generator is configuredto pulse the low frequency bias RF signal from the high state to an offstate, and wherein the high frequency RF generator is configured topulse the high frequency bias RF signal from the high state to an offstate.
 7. The system of claim 1, wherein the low frequency RF generatoris configured to pulse the low frequency bias RF signal during the lowTCP state from a low state to a high state, and wherein the highfrequency RF generator is configured to maintain the high frequency biasRF signal in an on state during the high TCP state.
 8. The system ofclaim 7, wherein the low frequency RF generator is configured to pulsethe low frequency bias RF signal from the high state to an off state,and wherein the high frequency RF generator is configured to pulse thehigh frequency bias RF signal from the on state to an off state.
 9. Thesystem of claim 1, wherein the low frequency RF generator is configuredto maintain the low frequency bias RF signal in an on state during thelow TCP state, and wherein the high frequency RF generator is configuredto maintain the high frequency bias RF signal in an on state during thehigh TCP state.
 10. The system of claim 9, wherein the low frequency RFgenerator is configured to pulse the low frequency bias RF signal fromthe on state to an off state, and wherein the high frequency RFgenerator is configured to pulse the high frequency bias RF signal fromthe on state to an off state.
 11. A controller for etching isolation anddense features within a substrate, comprising: one or more processorsconfigured to: control a low frequency radio frequency (RF) generator tosupply a low frequency bias RF signal to a first impedance matchingcircuit, control a high frequency RF generator to supply a highfrequency bias RF signal to the first impedance matching circuit, andcontrol a transformer coupled plasma (TCP) RF generator to pulse a TCPRF signal between a low TCP state and a high TCP state and to providethe TCP RF signal to a second impedance matching circuit, wherein theone or more processors are further configured to: control the lowfrequency RF generator to supply the low frequency bias RF signal duringthe low TCP state to etch the dense features; and control the highfrequency RF generator to supply the high frequency bias RF signalduring the high TCP state to etch the isolation features; and a memorydevice coupled to the one or more processors, wherein the memory deviceis configured to store a parameter level for the low TCP state and aparameter level for the high TCP state.
 12. The controller of claim 11,wherein the one or more processors are further configured to: controlthe low frequency RF generator to maintain the low frequency bias RFsignal in an off state during the high TCP state; and control the highfrequency RF generator to maintain the high frequency bias RF signal inan off state during the low TCP state.
 13. The controller of claim 11,wherein the one or more processors are configured to: control the lowfrequency RF generator to pulse the low frequency bias RF signal duringthe low TCP state to decrease an angular spread of high energy neutrals;and control the high frequency RF generator to pulse the high frequencybias RF signal during the high TCP state to decrease an angular spreadof ions.
 14. The controller of claim 11, wherein the one or moreprocessors are configured to: control the low frequency RF generator topulse the low frequency bias RF signal during the low TCP state from alow state to a medium state and from the medium state to a high state;and control the high frequency RF generator to pulse the high frequencybias RF signal during the high TCP state from a low state to a highstate.
 15. The controller of claim 14, wherein the one or moreprocessors are configured to: control the low frequency RF generator topulse the low frequency bias RF signal from the high state to an offstate; and control the high frequency RF generator to pulse the highfrequency bias RF signal from the high state to an off state.
 16. Thecontroller of claim 11, wherein the one or more processors areconfigured to: control the low frequency RF generator to pulse the lowfrequency bias RF signal during the low TCP state from a low state to ahigh state; and control the high frequency RF generator to maintain thehigh frequency bias RF signal in an on state during the high TCP state.17. The controller of claim 16, wherein the one or more processors areconfigured to: control the low frequency RF generator to pulse the lowfrequency bias RF signal from the high state to an off state; andcontrol the high frequency RF generator to pulse the high frequency biasRF signal from the on state to an off state.
 18. The controller of claim11, wherein the one or more processors are configured to: control thelow frequency RF generator to maintain the low frequency bias RF signalin an on state during the low TCP state; and control the high frequencyRF generator to maintain the high frequency bias RF signal in an onstate during the high TCP state.
 19. The controller of claim 18, whereinthe one or more processors are configured to: control the low frequencyRF generator to pulse the low frequency bias RF signal from the on stateto an off state; and control the high frequency RF generator to pulsethe high frequency bias RF signal from the on state to an off state.